The instant invention relates to bursting apparatus and more particularly to the separation (tearing) of a continuous web of material along transverse lines of weakening.
Forms of stationery are often preprinted on a continuous web of perforated material. Such forms are conventionally used in billing and other typical business transactions. The continuous series of forms requires processing for end use such as mailing. This may require bursting or separating the forms, as well as the performance of the end functions of stacking, stamping, sealing, inserting, collating (for additional enclosures) and folding. The aforesaid end functions are all provided for with existing equipment in one continuous process.
It is known from U.S. Pat. No. 4,261,497, issued Apr. 14, 1981, and assigned to the assignee of the instant invention, to use two pairs of feed rollers perpendicular to the path of travel through which the web is fed for the purpose of bursting the web. A breaker roller is located in the path of travel between the two pairs of feed rollers for increasing tension along the line of web perforations and causing the webs to rupture along that line. A magnetic brake and a magnetic clutch are connected to opposite sides of the first feed roller. The clutch and brake work together to slow and halt the first (upstream) pair of feed rollers at predetermined times, as controlled by an electronic timing circuit. Since the second (downstream) pair of feed rollers is driven at a constant and continuous rate of speed, severance of the webs is promoted along the line of perforations as the downstream rollers pull the web against the restraining force of the upstream rollers.
In U.S. Pat. No. 4,284,221 issued Aug. 18, 1981, a method of bursting a web having transverse lines of weakening is disclosed in which the speed of the upstream pair of feed rollers is reduced below the speed of the downstream pair of feed rollers (and/or the speed of the downstream pair of feed rollers is increased above that of the upstream pair of feed rollers) when a weakened portion is located between the two pairs of feed rollers. An electromagnet is used to regulate the speed of the feed rollers.
In today's marketplace, it is desirable to be able to maximize the throughput of the web. In the '497 patent, throughput is not maximized because the upstream pair of feed rollers is brought to a stop. In the '221 patent, throughput is not maximized because as soon as a line of weakening is located between the two pairs of rollers the upstream pair is slowed. The slowing of the upstream pair of rollers is obviously effected prior to the optimum time of slowing in terms of maximizing throughput.
The instant invention overcomes the problems associated with the foregoing problems and provides a method and apparatus for bursting a web of sheet material having transverse lines of weakening while simultaneously maximizing the throughput of the bursting apparatus.